1. Field of the Invention
The present invention relates to a cassette accommodating case for storing an audio magnetic tape cassette, and more particularly to a cassette accommodating case in which a magnetic tape cassette can be accommodated in either a forward or a backward orientation thereof.
2. Background Art
A magnetic tape cassette (hereafter simply referred to as a "tape cassette") which is conventionally used as an audio tape or the like has a front opening portion into which a magnetic head or the like is inserted when the tape cassette is loaded in a recording/reproducing apparatus or the like. The magnetic tape is wound in such a manner as to traverse the front opening portion. Accordingly, dust may enter the interior of the tape cassette through the front opening portion, and the dust may be adhered to the magnetic tape, causing poor magnetic recording and/or reproduction. Hence, the magnetic tape cassette is usually stored in a state in which it is accommodated in a cassette accommodating case (hereafter simply referred to as an "accommodating case") formed of plastic for the purpose of preventing the entrance of dust as well as protecting the magnetic tape exposed at the front opening portion and protecting the overall tape cassette.
FIG. 22 shows a conventional accommodating case. As a basic arrangement thereof, this accommodating case 1 is comprised of a cover section 11 and a casing section 12 rotatably connected thereto. The cover section 11 has a cover-side opposing wall 13 arranged to extend along one surface of a tape cassette 2 and a pocket 14 which is disposed on one side of the cover-side opposing wall 13 and into which a front opening portion 21 of the tape cassette 2 is inserted. As shown in the drawing, an index card 3 and the tape cassette 2 are capable of being inserted into and drawn out of the pocket 14 along the cover-side opposing wall 13.
The casing section 12 has a casing-side opposing wall 15 for covering the other surface of the tape cassette 2 loaded in the cover section 11, a pair of pivotally attaching portions 16 for rotatably connecting the casing-side opposing wall 15 to the cover section 11, and a pair of rotation-preventing projections 17 project from the casing-side opposing wall 15.
The pivotally attaching portions 16 are formed such that a pair of shaft-like projections, which are respectively fitted in shaft-receiving holes formed in both side walls of the pocket 14 of the cover section 11, are provided on corresponding inner side portions of the casing section 12, thereby connecting the cover section 11 and the casing section 12 in such a manner as to be rotatable with respect to each other. The rotation-preventing projections 17 prevent slackening of the magnetic tape during storage by engaging hubs 22 of the tape cassette 2 loaded in the cover section 11 when the casing-side opposing wall 15 is closed with respect to the cover section 11 when the latter is rotated about pivotally attaching portions 16.
Specifically, each rotation-preventing projection 17 is comprised of, for instance, a retaining piece 18 whose width is set such that opposite side portions thereof project between adjacent ones of hub pawls 23 which project from the inner periphery of the hub 22, as well as a pair of projections 19 provided perpendicular to the retaining piece 18 and whose opposite side portions face the opposing hub pawls 23, respectively.
The retaining pieces 18 and the projections 19 are shaped such that their upper end side is cut diagonally to facilitate fitting in the hub 22. The double-headed arrow (a) in FIG. 22 indicates the directions in which the casing section 11 is opened and closed, while arrow (b) indicates the direction in which the index card 3 and the tape cassette 2 are inserted into the cover section 11.
The entire tape cassette 2 can be accommodated in the accommodating case 1 if the cover section 11 is opened as shown in the drawing, the front opening portion 21 of the tape cassette 2 is accommodated in the pocket 14, and the cover section 11 and the casing section 12 are then closed together.
With the above-described arrangement, however, the direction in which the tape cassette 2 is inserted is limited to one direction, i.e., the direction in which the front opening portion 21 is accommodated in the pocket 14. Thus, the rotation-preventing projections 17 are designed so that the tape cassette 2 can be loaded into the pocket 14 from the front opening portion 21 side, which is herein referred to as "forward orientation", and if the tape cassette 2 is inserted erroneously in the opposite side with front opening portion 21 side, which is herein referred to as "backward orientation", the case cannot be closed, and the tape cassette 2 must be reinserted after correcting the orientation of the tape cassette 2 to the forward orientation.
Accordingly, arrangements shown in, for example, U.S. Pat. No. 5,168,998, Japanese Patent Application Laid-Open No. 4-311484, and European Patent 0 523 720A have been proposed as accommodating cases in which the tape cassette 2 can be accommodated in both the forward orientation and the backward orientation.
Such an accommodating case in which the tape cassette can be accommodated in either orientation has the following problem. Namely, the position where each hub 22 is formed is set such that a distance L1 from a front edge to a center axis of the hub and a distance L2 from a rear edge to the center axis are in a relation of L1&gt;L2, as shown in FIG. 23. Accordingly, the position of the hub 22 is offset in a case where the tape cassette 2 is inserted in forward orientation as shown in FIG. 2 and in a case where it is inserted in backward orientation. To describe this relationship with reference to a schematic diagram of the hub shown in FIG. 22 and FIG. 24, if it is assumed that the position of the hub 22 in the case where the tape cassette 2 is inserted in either one of the orientations is the position indicated by the solid lines, then the position of the hub 22 in the case where the tape cassette 2 is inserted in the opposite orientation is offset as indicated by the phantom lines. Hence, an interval W (a common area 4) corresponding to the difference, L1-L2, is the only space available for inserting the pair of rotation-preventing projections. For this reason, to prevent the magnetic tape from slackening by making use of the interval W, the rotation-preventing projection in terms of its shape must be formed into the shape of a tongue which is relatively thin.
The essential function of the rotation-preventing projections is to prevent the slackening of the magnetic tape, but the rotation-preventing projections in some cases also serve to position the tape cassette as they abut against the hubs. Particularly in the case of the type in which the tape cassette can be accommodated in either orientation, since the interval W of the common area 4 is small, the rotation-preventing projections have a relatively thin structure, and this may be problematic if the hubs and the rotation-preventing projections strongly abut against each other when closing the accommodating case. In the closing operation, after the tape cassette is inserted into the pocket of the accommodating case, the rotation-preventing projections move the hubs when the rotation-preventing projections enter the hub holes. Since the positional accuracy of the rotation-preventing projections is poor, a situation can occur in which the rear edge of the cassette is caused to float from the innermost portion of the pocket by the engagement between the rotation-preventing projections and the hubs. This increases the risk of the rotation-preventing projections becoming broken or the hub pawls becoming damaged, thereby causing a decline in the reliability of the accommodating case.
In addition, not only in the accommodating case of the type in which the tape cassette can be accommodated in either orientation but also in the type such as the one shown in FIG. 22, it is not desirable in terms of the function of cassette protection for the tape cassette to move with "play" inside the accommodating case. However, there has been a problem in that if an attempt is made to position the cassette without play by reducing the dimensions for accommodation by the setting of ribs which are formed on inner surfaces of side walls of the accommodating case, the parts become caught when, for instance, the accommodating case is closed, thereby causing a decline in the operating efficiency.
As shown in FIG. 25, the thickness W.sub.1 of the retaining piece 18 in the rotation-preventing projection 17 is far smaller than the interval W.sub.0 between adjacent ones of the hub pawls 23 of the hub 22. Because of this dimensional difference, even if the rotation-preventing projection 17 is engaged with the hub 22, the hub is capable of rotating in the range of W.sub.2 =W.sub.0 -W.sub.1. Due to this rotation, slackening occurs in the tape exposed in the front opening portion 21, or it becomes difficult to restrict the movement of the hubs since opposite side ends of the projections 19 are offset from the positions where they oppose the hub pawls 23. Hence, there has been a problem in that an undesirable shock acts on the hubs or the tape due to movement or play of the tape during carrying or the like.